In recent years, upgrade of the television broadcasting to the digital technology started in respective countries and areas including Japan, North America and Europe, and digital television broadcasting receivers that meet to broadcasting standards of the respective countries and areas are on sale. For example, in the case of the digital terrestrial television broadcasting, the following three standards are recommended, since contents of services and technological level at the time of introduction differ according to the countries and areas. A DVB-T (Digital Video Broadcasting-Terrestrial) system is adopted in Europe, an ATSC (Advanced Television systems Committee) system is adopted in U.S.A., and an ISDB-T (Integrated Services Digital Broadcasting-Terrestrial) system is adopted in Japan. In China, such a standardization process based on the DVB-T system adopted in Europe is advanced.
All of video and audio compression systems adopted in the above-mentioned standards conform to an MPEG-2 standard. Transmission systems also conform to an MPEG-2_TS signal (Transport Stream) standards. Accordingly, interfaces and circuits provided to a video and an audio decoder in the DTV can be commonly used in all of the countries and areas. If described in detail, compression systems such as the MPEG-2 currently adopted in the digital television broadcasting and an H.264 of ITU expected to be adopted in the future basically use an algorithm in which a motion vector is detected and a motion is predicted for coding. A decoder for decoding a video signal and an audio signal compressed according to these systems can be realized using a single hardware, a CPU and software operated on the CPU. Any differences among detailed specifications in the respective systems can be dealt with by changing the software. Accordingly, in the case of a subsequent circuit, that is a hardware circuit of the decoder, provided at the subsequent stage of a demodulator for demodulating a received signal into the MPEG-2_TS signal, manufacturers of the relevant module can commercialize a decoder commonly usable in the world to increase an effect of mass production.
On the other hand, a circuit relevant to such processings that are executed by the time when a television broadcast wave signal received via an antenna or the like is demodulated into the MPEG-2_TS signal, is called a front-end circuit. A tuner and a demodulator in the front-end circuit often largely depend on radio-wave policies peculiar to the respective countries and areas, and the respective countries and areas adopt different systems. With regard to a demodulation system used in the demodulator, a QAM system (Quadrature Amplitude Modulation) system is adopted in the DVB-T system and ISDB-T system, and a VSB (Vestigial Side Band) system is adopted in the ATSC system.
A CA (Conditional Access) part provided between the front-end circuit and the decoder operates integrally with an external conditional access module (referred to as a CA module hereinafter). In the CA part, since the CA part relates to businesses, different encryption systems and interface specifications with respect to the CA module are often employed in respective business areas and markets. A CI (Common Interface) system is adopted in the DVB-T system, a CableCARD interface is adopted in cable television broadcasting conforming to an Open Cable Standards in U.S.A., and an IC card interface is adopted in the ISDB-T system. These interfaces connect thereto such CA modules having different physical and electrical specifications in terms of terminal specifications. Accordingly, manufacturers of the digital television receiver have conventionally combined the decoder commonly usable in the world, front-end circuit modules for the respective countries and areas, and the CA parts for the respective markets, so as to commercialize digital television receivers having different configurations for the respective markets, and ensured operations thereof.
The CI is described in the Non-Patent Document 1, the CableCARD (formerly called POD) is described in the Non-Patent Document 2, and the IC card interface is described in the Non-Patent Document 3.
On the other hand, an attempt for complying with a plurality of markets by combining the CA parts is examined (for example, see the Patent Document 1). In the Patent Document 1, there is provided a plurality of CA module interfaces capable of connecting to respective CA modules. In addition, the plurality of CA modules are connected in series to each other.
Patent Document 1: Japanese patent laid-open publication No. P2000-36820A;
Patent Document 2: International application publication No. WO01/047267;
Non-Patent Document 1: EUROPEAN STANDARD EN50221, Common Interface Specification for Conditional Access and other Digital Video Broadcasting Decoder Applications, English Version, Ref. No. EN50221:1996E, February, 1997;
Non-Patent Document 2: AMERICAN NATIONAL STANDARD ANSI/SCTE28 2001 (Formerly DVS 295), HOST-POD Interface Standard, Engineering Committee Digital Video Subcommitte, Society of Cable Telecommunications Engineers, 2001;
Non-Patent Document 3: ISO7816-1 Standard, asynchronous smartcard information, Version 1.00, last revised on Jun. 12, 1995;
Non-Patent Document 4: PC Card Standard, Volume 2, Electrical Specification, PCMCIA/JEITA, 2001; and
Non-Patent Document 5: SCTE40 2001 (Formerly DVS 313), Digital Cable Network Interface Standard, Engineering Committee Digital Video Subcomittee, Society of Cable Telecommunications Engineers 2001.